Why do people speak in innuendo when they're on a date. Why do dictators try to squelch protests, Why do we join up with bullies to gang up on an outcast. Why do humans stand out from the rest of the animal kingdom by blushing and laughing and crying? And what does any of this have to do with George Costanza or when Harry met Sally, or anonymity on social media or cancel culture, or why we generally don't say everything
we mean. Welcome to Intercosmos with me David Eagleman. I'm a neuroscientist and author at Stanford and in these episodes we sail deeply into our three pound universe to understand why and how our lives looks the way they do. Today's episode is about a phenomenon known as common knowledge, which is something that I know and you know, and
we both know that we know it. Now, this could seem like a very particular sort of thing to pay attention to, but many psychologists and economists over the past decades have started to think that a deeper understanding of common knowledge could explain all kinds of things about human nature and behavior and societies, and for a very long time.
This has grabbed the attention of my friend and colleague Stephen Pinker, who just this week has a new book coming out on common knowledge called When Everyone Knows That Everyone Knows, And so I called him up to discuss this topic. I'll take just a moment to frame this before I begin the interview. At the heart of the issue is that we are a massively social species. We form lifelong relationships, and we join clubs, and we're parts
of tribes, and we're citizens of countries. And we're also a highly intelligent species, and we spend a lot of our time, usually unconsciously, figuring out who knows what and what we know in common, and for that matter, thinking about how we can expand common knowledge with the right signals, and often how we could hide things from becoming common knowledge. The key thing to understand for today's conversation is that common knowledge is not just about a bunch of individuals
each knowing something. It's that each person knows it and knows that everyone else knows it, and knows that everyone else knows that they know it, and so on. And the argument is that it's this ladder of shared awareness that allows societies to coordinate. Think about something like the game of chicken, where two drivers speed towards each other. Each knows the situation, but the critical factor is whether both drivers know what the other is willing to do,
and whether both know that the other knows. And the effects of common knowledge stretch from two people all the way up to countries. For example, history is filled with moments when private thoughts turned into common knowledge and changed the world. So, for example, in nineteen eighty nine, East Germans had long doubted the regime, but it was only when tens of thousands gathered in the streets when everyone could see that everyone else had the same doubts. That's
when the Berlin Wall fell. Stock Market bubbles and crashes run on the same sort of principle. Investors don't care only about the value of a stock, but about what everyone else believes everyone else believes about its value. So this is the type of thing that Pinker's book explores, all all the ways in which common knowledge permeates everyday life. Common knowledge, for example, is why etiquette works. You don't just know the rules, you know that others know them too.
It's why red lights function not because you fear the police, but because you know that everyone else knows the rule and is going to stop. It's why children learn to play Peek a boo, because the delight comes from that shared loop of I know that, you know that I'm here. So today we'll explore the phenomenon of common knowledge. Stephen Pinker is a cognitive scientist and linguist at Harvard and he's a longtime bestselling author who is famous for illuminating
the hidden structures of human thought and society. His new book dives into the puzzle of common knowledge, how it arises, why it matters, and what it reveals about the architecture of our social minds. Stephen joins me, Now, so, Steve, we are an intensely social species and there's a lot that has to happen in order to get us to coordinate as a result. And this is the thing you've been thinking about, So tell us how do we coordinate as a species.
Well, any two agents who need to coordinate need common knowledge. The theme of the book, common knowledge, being the state where I know something, you know it, I know that you know it, you know that I know it, I know that you know that I know that you know it, ad infinitum. Why Because it isn't enough for each party to know what the other one is going to do, because the other party guessing what the first one is going to do may do something complete different. So just
be concrete. If we're going to rendezvous and we don't generate common knowledge by a conversationalist, and my cell phone goes dead, so each of us asked to guess where the other one is going to go. It's not enough for me to know that you like to go to Starbucks, because you may know that I like to go to Pete's. And so if I go to Starbucks, that's where you're going to go. You might go to pizza because you
think that's where I'm going to go. And well, I know that, okay, so I'll go to Pietz because Dave knows that I like to go to pizza. But wait a sec Dave knows that I know they likes to go to Starbucks, so he's going to go to Starbucks after all, and so on. Nothing short of actually blurting it out in each other's presence will get you on the same page. Some kind of public perceptible self evidence signal. That's what is needed for coordination.
You've, of course spent much of your career studying language, and so you see language as one way of establishing that common knowledge give us a sense of that, Yeah, you know that.
I'm trying to get you to believe something because you know that I'm saying something with the intent that you believe it. That's kind of what language is. So it's a common knowledge generator when it is something is blurted out. What got me interested in this whole topic is actually almost the converse cases in which we try to avoid common knowledge when we don't say something in so many words, but we put our meaning between the lines. We count
on our reader to connect the dots. We use euphemism or innuendo or hinting or beating around the bush or hilly shallowing, which is a lot of language. That's one of the reasons it took so long to get computers to understand language. If you simply parse who did what to whom based on the subject of the verb and the object, you're really not going to understand what people actually meant, such as if you could pass a salt, that would be awesome. Okay, now think about that. I mean,
that doesn't make it much sense. It would literally be awesome, And you know, it's not like you're just pondering possible worlds. That's not the meaning. Everyone knows what the meaning is. It's give me the salt, and a lot of languages like that, and linguists have long known it. But the question is why what do we try to accomplish when we avoid blurting something what we want out? In so many words, what I suggest is that the we're avoiding
common knowledge. That is, each one knows what the other one is doing, but you may not know that the other one knows that you know that they know, and that allows you to preserve a certain relationship, relationships being coordination problems, as we mentioned at the top of the conversation, a relationship like being friends, being lovers, being a supervisor in supervisory, being transaction partners. Those are all matters of
common knowledge. We're friends not because we signed a contract, but because each one knows that the other one knows that there we're friends, and that can be threatened by certain things that could become a common knowledge that contradict the basis of the friendship, like a sexual proposition. So why do people say things like I want to come up for Netflix and show, or you want to come up for coffee when you know, though you know, let's say it's a man saying it to a woman. You know,
she wasn't born yesterday. She's a grown up, she knows what it means. But it's still way better than Hey, you want to come up and have sex, which would be you know, both parties. You are pretty uncomfortable, even though would you like to come up for coffee? Doesn't make them uncomfortable? How come that was the problem that I took up in a previous book, The Stuff of Thought.
Language is a Window into human nature, which had a chapter called games People play on language as a window into social relationships and in trying to figure out why we don't just blurt out what we mean. Other examples being say a failed bribe. Let's see you trying to jump the queue in a restaurant and you slip the major DA twenty dollars bill and say, I just wondering if you might have a cancelation, or this is an important night from you. Is there any way to shorten
my weight? Why don't people just say if I give you twenty dollars, will you see me? Right? Away or fundraising. I've seen this a lot at Harvard. I'm sure you've seen a similar thing where the dean will say to the rich people in the audience, we're counting on you to show leadership, to be a friend to the university instead of the reason we're all here is you're going to open your checkbook and write, you know, a check for five million dollars. That's another case where people don't
say what they mean. Why not? And here's the answer that got me interested in common knowledge. And I've done studies to back this up that if it's do you want to come up for coffee? Well, you know, she knows what he means, and you know obviously he knows what he means. But does she know that he knows that she knows? With an innuendo like would you like to come up for coffee, she could think, well, maybe he thinks I'm naive, and if I said no, maybe
he thinks, you know, caffeine would keep me up. Even though she knows that she's turned down a sexual overture, he knows it as well, but he could not know why because she knows that he knows. And likewise he could think, well, you know, maybe she thinks I'm dead, Maybe she thinks that I think that she's just turned down coffee. Uh. They can maintain their platonic friendship with
the common knowledge that it's just about companionship. Whereas he said you want to come up for half sex and she said no, they can never be platonic friends in the same way. Again, the intuition is it's out there, you can't take it back, And I suggest that technically what's happening is that the blurted out speech generates common knowledge.
Common knowledge is the basis of our relationships. Their coordination, games, euphemism and innuendo get a message across without generating common knowledge, and that's why we fall back on it so often.
Okay, so that's how we sometimes try to mask common knowledge. Tell us about how common knowledge is useful in society, society wide, let's say, with public demonstrations and politics and economics.
Yeah, a lot of our large scale coordination, not just two friends or Roande going for coffee or agreeing to be platonic friends, but large scale things like everyone recognizing money, Like why do I accept a green piece of paper in exchange for something of value? Well, because I know that other people will accept it and give me something of value. Why would they do that, Well, they know that still other people would accept it. So the value
of currency depends on common knowledge. Everyone knows it's worth something, and that's what makes it worth something. The fact that everyone knows that everyone knows it. A lot of power depends on common knowledge. There are laws, there's courts, there's a police force, there's a jail. But most of the time people just follow the law, even though big brothers watching them twenty four to seven. However, these things can change.
It's not easy to change them when the basis of power or money is just common knowledge, because everyone has an interest in keeping up the common assumption. But sometimes it can unravel. In the case of power, if there is a public protest, everyone shows up at a public square at the same time, the same place, everyone sees everyone else there. Previously, maybe that everyone was resentful of
the system, thought it was inefficient and oppressive. They may even have suspected that everyone else had the same feeling, but they didn't know that other people knew that. They knew they couldn't coordinate by all rising at the same time, and so the regime could keep them in their place by preventing common knowledge. And that's why dictators don't allow freedom of assembly, freedom of the press, freedom of speech, precisely because they're afraid that people coordinating which they could
only do with common knowledge, could acting together overpower a regime. Likewise, in the case of going back to money again, if the value of money depends on common knowledge, then when the common knowledge is threatened, the value of money can disappear.
And that's what happens when you get hyperinflation, people taking home their wages in a wheelbarrow because no one will accept it anymore, or a bank run where people withdraw their savings, not necessarily because they think that there's anything wrong with a bank, but as long as there's a rumor that other people think that there's a problem with the bank, and they're withdrawing their money out of fear that still other people will withdraw their money, it suddenly
becomes rational to withdraw your money while the bank still has money to withdraw. And that can cause a bank to fail, that can cause the whole economy to fail. That's what happened in nineteen twenty nine. And so when Roosevelt said the only thing we have to fear is
fear itself. He was stating a theorem of common knowledge that was quite literally true, that what people had to fear was fear itself, and the fear of fear, the recursive fear, the common knowledge, could actually change the value of those financial institutions.
So here's something I wanted to dig in with you about after reading your book. How do we think about false common knowledge? By which I mean, let's imagine that you and I engage in a public protest and we look around and we see a thousand people around us. We say, look, everybody clear feels this way, but we're not aware of that across town there's a larger protest with ten thousand people in it, and we have the impression that everyone feels the same way we do about something.
I mean that technically be common belief rather than common knowledge, But different pools of people can have different common beliefs, and there can also be common misconceptions where prior to the protest, there are cases where people think that everyone else believes something. In fact, everyone could believe that everyone else believes someone something and no one actually believes it, sometimes called a pluralistic ignorance. Or a spiral of silence.
What's an example of that.
A classic case study of pluralistic ignorance in social psychology was when some psychologists interviewed the guys in the fraternity. They found that every one of them thought that it was really stupid to drink so much that you pass out, but everyone thought that all the other frat bros thought it was cool. No one actually thought it was cool, but that all the others thought it was cool. And
there are probably a lot of cases like that. I mean, an extreme case would be The Emperor's New Clothes, where everyone thought that everyone else thought that who were seeing clothes, no one actually saw clothes, And it took the little boy blurting it out generating common knowledge, for the common misconception to flip into common knowledge. The Emperor's New Clothes
is a story about common knowledge. The boy wasn't telling anyone anything they didn't already know, but it was changing the state of their knowledge because now everyone knew that everyone else knew, and that changed their relationship with the Emperor from a deference to scorn and ridicule.
I do worry a little bit, though, about people assuming politically common knowledge and saying, Hey, if I just make some innuendo, everyone will understand what I mean by this, because that often doesn't work, especially now.
Well, the thing about innuendo is that it has to be calibrated so that it is recognized by a kind of willing recipient, but can be denied by an unwilling recipient. So it has to be calibrated in that zone, and there can be errors in either direction. Where there's an episode of Seinfeld where George Costanza is invited up for coffee and says no because he's got to get to work early the next morning, and then as he's walking out, he says, oh, my god, coffee doesn't mean coffee. Coffee
in sex. So there's the Costanza problem that it could be so subtle that it goes over the head, or there could be conversely, it's so blatant that the the unwilling hearer calls you on it again. You know, all of these things, by the way, are worked out in fiction,
in comedies, comedies of manners, situation comedies. They kind of allow us to exercise our facility for recursive mentalizing, that is, getting inside the head of other people, getting inside the head of other people and so they're often worked out that so often were drives fictional plots. But the opposite is when when Harry met Sally, and Harry, you know, early on, is kind of complimenting Sally and they just met kind of a little too insistently, and then she
blows the listle. She says, you're coming on to me, which leads to a wonderful discussion of common knowledge. I mean, not not in those words where he says, okay, let's say I was coming on to you. What are we going to do? I take it back? Okay, I take it back, and she says, you can't take it back. He says, what do you mean you can't take it back? You know, what are we going to do? Call the cop and she says, it's out there. It's too late, So it's out there. That is a metaphor for common knowledge.
That is something that's out there, is something that you see other people see, you see them see it. And direct speech or even in this case, indirect speech that was not indirect enough. It kind of exceeded that. The cutoff is out there, and when it's out there, it changes the nature of the relationship. They were no longer just near strangers, platonic friends. He had turned it into a sexual relationship, which you rebuffed.
Great, So I want to return for just a second to literature, which you mentioned fictions, because I made the argument on this podcast little while ago that I'm not so worried about AI completely taking the job of writers. And I listened five different reasons, but one of them had to do with the fact that we could all generate totally bespoke literature, just like Kings of Yesteryear would do. But we lose something there, which is that a big part of literature is the social glue, the fact that
everyone else has read the same story. I don't want my Game of Thrones to have a different outcome than your Game of Thrones. So my question to you is, what is the reason we desire common knowledge so much?
I think it's a great example, and people may not remember that back in the nineties, when the internet first became a thing, there was the idea that you could dial in whatever ending to a story you wanted. That fiction would be, movies would be the same. Everyone could watch that movie. Maybe let's they didn't take off. And I think it's the reason that you identified, namely part of the experience of art is that it's common knowledge.
You know about something at the same time you know that everyone else knows about it, and that's what gives you something in common that can reinforce a social relationship. With friendship, a movie with friends, you talk about it with friends, and the common experience is one of those things that kind of go makes friends friends. They go
through things together, they share common interests. The basis, the common knowledge, that's the tacit basis of friendship is that we're kind of there's a kind of a mind mild, even a you know, a body meld, where that we are in physical proximity, We hug, we shake hands, all the more intense and romantic relationship.
Okay, So I want to return and dig in just a little on this point because I'm fascinated by this about false common knowledge what I'm calling that or a misconception about it. So, for example, recently, Charlie Kirk was assassinated in broad daylight, and if you look on X and if you look on blue Sky, you find very different stories about that. And presumably the people who are tweeting or blue skying are thinking, hey, this is great. We have shared common knowledge. But you in fact have
two groups of people. I'm exaggerating a little bit the difference, but you have different groups that have beliefs that they believe are shared by everybody. Just one second example. This My grandmother I remember many years ago in Florida said I can't believe that so and so just one governor, because I don't know anybody that voted for him. And it was true, of course she didn't know anybody, but it doesn't mean that the majority of the state didn't vote for him.
Nonetheless, Yeah, I mean common knowledge, or more accurately, in a lot of these cases, is common belief, That is, you believe something, you believe that other people believe that you believe it, and so on. Is relative to a network, a community which can be disconnected from another network, and the common knowledge is often generated since none of us experience everything firsthand. In fact, on for politics, we experience almost nothing firsthand, and we read about it, we hear
about it. If the sources are disjoint, then the pools of common knowledge within each of these networks could be disjoined. And that happens partly from social media, as even feeds within a platform, but even more so when they're different platforms like X versus Blue Sky, or in the case of cable news, do you watch Fox News or do
you watch CNN or do you watch MSNBC. So one of the users I take up in the book, and this intersects with my interest in academic freedom and freedom of speech in another part of my life where I co founded and I'm the co president of the Council and Academic Freedom at Harvard. Why is free speech so important and all the more so in a country? Why is freedom of speech enshrined in the First Amendment to the American Constitution, Freedom of the press, freedom of assembly.
So what is it about speech that can be so threatening to a dictator? You might think, Well, the dictator would be tend to let people bitch and moan all they want. He's what with the guns, And as Mao said, power comes out of the barrel of a gun. So why should a public protest or a critical editorial be
so threatening to a dictator? Well, the reason is, as Gandhi said in the eponymous movie, he says to a British officer in the end, you will leave because there's simply no way that one hundred thousand Englishmen can control three hundred and fifteen million Indians if the Indians refuse to cooperate. So that's just a truth about numbers then, But it raises the question, how do you get three
hundred and fifteen million people cooperating or in this case coordinating. Well, some public event demonstration where you're protesting, you can see everyone else protesting, and everyone can see everyone else. You know, the time is now a prominent public uh declaration you know, Jacques or an article. Everyone knows now that it's public that everyone hates the regime and people can, you know, either storm the palace or just refuse to work or
to cooperate. And so dictators don't want that to happen. They want to prevent the generation of common knowledge, which is why police states control both public assembly and public media. I give a joke. I recount a joke from the era of the Soviet Union in which a man is handing out leaflets in Red Square and of course they're sure enough the KGB arrested. They take them back to headquarters, only to discover that these leaflets are blank sheets of paper,
and they think, what is the meaning of this? And he says, what's there to say, it's so obvious. So that's a joke about common knowledge. Namely, he was being subversive because by the very act just handing out leaflets didn't matter what they said. That now everyone who accepted the leaflets accepting seeing everyone else except the belief that they all knew that there was something to protest, and they didn't have to be told what it was because
they knew privately what it was. The act of communication was that giving it out in a public square made the private knowledge common, and that was threatening to the regime, which is why, in a case of life imitating a joke, Putin's regime has arrested people for carrying blank science.
I'm sorry to return to this point, but if you stood on a street corner and said I'm protesting, and you handed out blank sheets of paper, the lefties would think one thing from the blank sheet, and the right's would think another thing. And so in an ideal sitution, I mean, we look at the Soviet regime as a failure, and so we say, okay, it was obvious what he meant by that. But I'm interested in the fact that
we each have very different internal models. Let's say, with politics and so the transmission of common knowledge isn't so easy in a sense.
Well, yes, I mean it depends on a conspicuous public signal and in general from a trusted source and who trusts who can vary between interconnected but disjoint networks of people. But it's not, you know, it's not the case that everyone goes that own way. Otherwise we wouldn't have society, we wouldn't have science, we wouldn't have markets, we wouldn't have currency.
But we do have parties. We do have two different parties that increasingly disagree more and more we do.
Yes, I mean that, As I said, there can be the common belief within semi disconnected networks, within each of which you have common belief, but not necessarily in the the entire group. The general phenomena are that common knowledge is generated by public signals that people see when they know that everyone else sees sees themselves seeing it. And again that can be relative to pop the population and the connected network that sees each other seeing something at the same time.
So tell us about cancel culture and also why cancel culture is more possible in a world where people can hide behind keyboards.
Yes, I have a chapter in the book called the Canceling Instinct, and it does touch on my interest in academic freedom, but the point of the chapter isn't so much to make the case for academic freedom, though I do reprise that, but as a psychologist, to ask, why is there an urge to censor, to cancel, to punish people for their opinions. Now, of course that's been true for all of human history, or heretics have been burned
at the stake or crucified. But you think that in universities of all places, for the arena where we ought to be, not treat beliefs as sinful. May be mistaken, maybe illogical, but then you point it out, why do you try to destroy the person who's ventured that opinion. That's the phenomenon of cancel culture, and I suggest it's because a combination of two psychological phenomena. One of them is that even though the whole basis of science and scholarship is there is a truth, we have means to
try to approach it. We may be mistaken, but we're not bad people because we're mistaken. That you believe things to the extent that there's good evidence for, good arguments for it, that whole complex of beliefs is kind of
weird in human history. And the more common attitude is for most people most of the time, is your beliefs are a reflection of who you are, whether in particular what tribe you belong to, and whether you're a good person, who usually means upholding the sacred beliefs of your tribe. Now that is poison for science and for scholarship and
for academia. But it is the way that people think that the beliefs I mean putting aside beliefs about here and now, I mean there are you know, people don't hallucinate. They know, you know there's food in the fridge. There isn't food in the fridge. But when it comes to more bigger questions, where did humans come from? Why is their disease? Why are their revolutions? Why is their wealth and inequality? Things that we academics tend to think can
be answered by the methods of science and scholarship. But most people is what you believe signals what tribe, what coalition you belong to, And you're bad if you have the wrong belief So if you have that kind of built in flaw in human belief, then there can be norms as to what you believe in what you don't believe. And norms are matters of common knowledge. They exist because people believe they exist. They can be threatened if people flout them and get away with it. So and we
have everyday social norms. You don't go around naked, you don't make you pass gas in public, you don't tell ethnic jokes anymore, you don't insult people's appearance to their face. All these norms are held up just because it isn't done, and everyone knows that it isn't done. Conversely, if it is done, the norm can unravel. So people often feel the need to prop up norms by if noting when they're flouted in public and then punishing the violator in public.
And the punishment has to be public for it to prop up the norm, which is why we used to have public hangings and pillories and stocks and crucifixions. Only if you have everyone seeing that the person is punished, could the norm survive well. I think we now have an equivalent, often an electronic equivalent, in social media, where if someone does flow a norm, that is, they express an opinion that goes against what you take to be
the moral convictions of your tribe. People feel the urge to punish it in public, and that's really easy to do on social.
Media and the anonymity of being behind the keyboard. I think, you know, it's just like the trolley dilemma, where if you have to push the person with your hands, it's different. You activate these motional networks and you're less likely to do that. But if you have to pull the lever so that only one person gets killed instead of five people, then most people are perfectly willing to do that at a distance. And it strikes me it's the same thing with the anonymity.
Well, that's right. And it also and this does relate to another common knowledge phenomenon, that is that our social relationships. Are we friends? Are we lovers? Are we boss and subordinate? Are we neighbors, members of a civil society? A lot of these are reinforced by common knowledge generators. Eye contact, handshakes, laughter, blushing,
eye contact, things that can't be denied. That is, you look someone in the eye, you're looking at the part of them that's looking at the part of you that's looking at the part of them that's looking at the part of you, ad infinitum. So it's an eye contact is a common knowledge generator, and the common knowledge that these signals generate tend to be things like, well, we're
all acting like we're members of a community. So indeed, when those signals are present because you're face to face, then that can restore the norms of how you deal with a person in a peer group, namely, you don't insult them to your face. Without those common knowledge generators, such as in the anonymity of a keyboard, then you can insult people, you can denigrate them, you can try to destroy the reputations in a way that would be kind of unthinkable in a face to face situation.
There's one piece I want to return to about cancel culture, which is why everybody jumps on the bandwagon. You had a section in your book about moral condemnation and why it's better to join the bullies than to take the risk of being bullied.
Yeah, yeah, give us a sense exactly. I mean, it's a kind of a playground dynamic that many of us remember sometimes with shame, when we may have joined the bullying mob and out of fear of becoming the kid that everyone picks on and there is there's an equivalent in academias. I had to say where I mean, it has no place because we're all in it together trying to find the truth. But you get the instant petition with six hundred signatures, which can usually gin up on
social media. There are enough grad students in the country that you can get get this is to sign some condemnatory petition. But I think it is some of the same dynamic, and there is a dynamics. Sorry to keep relating things to common knowledge, because it is the theme of the book, the theme of our conversation, but I do think that it governs many human interactions. There's a theory from a former post doc online Peter to Sholey and his former advisor Rob Kurzband that we know no
one is an island. We really want to be part of some group, some posse, some band of brothers, because you know we're sitting ducks. If we're isolated, how do you know which group to join? You don't want to be on the losing side. If you can find some sin that someone has committed and you all jointly recognize that they are a sinner, they've broken some norm some law, you gang up on them. That's a and it's common knowledge as you know that the other people recognize that
same violation. It is a basis for forming a coalition, and people often will band together and to single out some victim as and there's something that feels right about being in that band, and it is the basis that the coalitions could form and the target suffers their kind
of collateral damage. Probably the episode from fiction that kind of draws that out of the most is the famous story by Shirley Jackson called The Lottery, came out in the late forties, often assigned in high school and debated ever since, where the town folk of a Bucolic village every year choose someone by lottery and stone to death as a person, suggesting that there is some kind of human urge to simply gang up on a victim and
they in this case. What makes the story so chilling and so kind of absurd is the victim didn't actually do something other than being the loser in the lottery. But what it kind of played out, what continues to make it fascinating is this dynamic of being part of a mob united in its victimization of a victim.
Yeah, so it doesn't only have to do with the violation, It has to do with the social bonding that results. Okay, great, what else should everybody know about common knowledge?
Yes? Well, one of my favorite chapters, the one that I had one of the most fun writing, was the one on body language social signals laughing, crying, blushing, staring, glaring on signals that I think we fall because they were common knowledge generators. So in case, you know, why do we blush? The mark twains and men is the only animal that blushes or needs to and he was he is right that men are. You know, humanity is the only animal that plushes. There are other things that
also that make humans unique. We're the only species that that weeps. We're the only species that laughs. There's a kind of precursor in chimpanzees in a kind of panting that a companies play fighting. But you know, it's not like are exactly the same as our laughter. We are. Eye contact is really important to humans, and that's probably why we evolved a white sclera, the whites of our eyes that other primates don't have. Why we have elongated eyes so that our position of our eyes can easily
be discerned. So all of these I suggest are effective because they when you express them, the perceiver knows that you know that you're expressing them. So in the case of blushing, you feel the heat of your cheeks from the inside at the same time that you know that other people can see them redden from the outside and
they know that you're feeling it. Because what makes blushing so painful is knowing that other people know that you're blushing, as when people say you're blushing, which makes people blush all the more and can even make them blush if they're not blushing, you know, or or tearing up weeping. You're seeing the world through the kind of the scrim of your own tears, and other people can see the
glisten or the trickle of your tears. So these are cases where I think you're establishing something about your relationship with the person in a involuntary, unfakable, and undeniable way. In the case of blushing, it's I know that I've screwed up by the norms that you hold, and so even though I've screwed up, better that I know that I've screwed up than that I just blow off your norms as if I was some kind of loose cannon or weirdo or psychopath. In the case of crying, it's
I acknowledge, defeat, surrender, helplessness. I'm not going to fight back. It's going to be bodily equivalent of raising a white flag or throwing in the towel in a boxing match. Anyway, I talk about each one of these displays and why I think they evolved as a common knowledge generator in order to ratify a certain kind of social relationship.
Excellent, Yeah, I love that chapter. Okay, any closing thoughts about common knowledge?
Yeah, just is. I think it's a missing piece of the puzzle of a lot of human life that a lot of would seem to be arbitrary. Rituals, conventions, hypocrisy do have a hidden rationale in terms of either generating or denying common knowledge, including all of the ways in which we are systematically hypocritical, genteel, polite, dainty. We don't blurt out things that all of us know privately but we don't know commonly, and there's a reason for that.
It's necessary to preserve and retain certain social relationships on which social life depends, and that, as certain comedies point out where they envision a world in which someone or everyone is forced to be honest. It quickly becomes a dystopia, and the characters are glad to go back to a state in which you don't say everything that you need.
That was my interview with Stephen Pinker. His new book is called When Everyone Knows That Everyone Knows, Common Knowledge and the Mysteries of Money, Power, and Everyday Life. The book tackles many mysteries of life and psychology centered on this question of how humans manage to coordinate on scales that range from two drivers in a game of chicken to millions of people in a nation. A lot of the answers lie in this recursive loop of awareness that
we call common knowledge. Pinker shows us in the book that common knowledge is at least some of the engine behind laughter, applause, etiquette, trust, diplomacy, and financial markets. And common knowledge is the difference between a thousand private doubts and a public turning point in history. Private knowledge lives in our skulls, but common knowledge spills into the shared spaces between us, and it's what transforms isolated individuals into
a civilization. In our daily lives, we hardly notice it, but every time that we have on the correct side of the road, or laugh at the same moment in the theater, or rise to our feet in a standing ovation. We're participating in a recursive dance of shared awareness. The thing that's so striking is how invisible it generally.
Is to us.
But common knowledge is the thread that binds strangers into this mad, wild, beautiful collective that we call society. Go to eagleman dot com slash podcast for more information and find further reading. Join the weekly discussions on my substack and check out Subscribe to Inner Cosmos on YouTube for videos of each episode and to leave comments until next time. I'm David Eagleman, and this is Inner Cosmos.